POS0913 LOW ADDITIVE VALUE OF A REPEAT MRI EXAMINATION OF THE SACROILIAC JOINTS WHEN THE FIRST MRI IS INCONCLUSIVE
Authors: I. Eshed, T. Goitein, M. Lidar
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Diagnosing sacroiliitis on MRI of the sacroiliac joints (SIJ) is not always straightforward. It is common practice in inconclusive cases to repeat the MRI after a variable period of time with an expectation that more conclusive acute/structural lesions will develop and allow for an irrefutable diagnosis of sacroiliitis. <h3>Objectives</h3> To evaluate the diagnostic utility of a repeat SIJ MRI following an initial inconclusive MRI examination. <h3>Methods</h3> Subjects with &gt;1 SIJ MRI examinations, where the index scan was inconclusive for sacroiliitis and ≥ 6 months' interval has elapsed between scans, were included. Repeat scans were evaluated for the presence of structural/acute SIJ lesions and were accordingly diagnosed with either sacroiliitis or another applicable diagnosis. Clinical data was extracted from the patients' clinical files and by a telephone questionnaire. Diagnoses and scores were compared between index and follow-up examinations (t test). <h3>Results</h3> 71 subjects were included in the study; 77.4% females, mean age 41.0±15 years. Mean time interval between exams 30.4 ± 25.24 months. 12 subjects performed &gt;2 scans. Clinical information was available in 63 subjects (86%) and is summarized in Table 1. In only two subjects (2.81%), both females, MRI diagnosis changed from inconclusive to definite sacroiliitis on the follow-up scan; a 41-year-old patient that had inflammatory back pain for two years prior to the index MRI, had peripheral arthritis but no family history of SpA and a 39-year-old patient with inflammatory back pain since the age of 23 years and an elevated CRP but no family history of SpA or other clinical rheumatic involvement. Final diagnosis after the 2nd MRI was osteitis condensans illi in 29 patients, DISH in 3 patients, degenerative changes in 6 patients (two accompanied by enthesitis) and enthesitis in 1 patient. In 10 patients (14.1%) diagnosis was still inconclusive after the 2nd MRI examination. No major abnormality was found in the follow-up MRI examination in 20 subjects. None of the subjects with &gt;2 scans, had evidence of sacroiliitis in any of the following MRI examinations. <h3>Conclusion</h3> Repeating SIJ MRI examination when index MRI is inconclusive is of minimal additive value. When MRI findings are inconclusive, decision making should be based on clinical data. <h3>References</h3> [1]Lukas C, Cyteval C, Dougados M, Weber U. MRI for diagnosis of axial spondyloarthritis: major advance with critical limitations 'Not everything that glisters is gold (standard)'. RMD open 2018;4 1: e000586. [2]van Onna M, van Tubergen A, Jurik AG, van der Heijde D, Landewe R. Natural course of bone marrow oedema on magnetic resonance imaging of the sacroiliac joints in patients with early inflammatory back pain: a 2-year follow-up study. Scand J Rheumatol 2015;44 2: 129-34. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Iris Eshed Speakers bureau: Novartis, Abbvie - lecture fees, Tamar Goitein: None declared, Merav Lidar Speakers bureau: Abbvie, Novartis.